The present invention relates generally to a tension control mechanism for a chain or other flexible drive member for a self-propelled power tool and, more particularly, to a tension control mechanism for a chain or other flexible drive member for a self-propelled aerator.
In the field of landscaping, turf aeration (“aeration”) is the process of mechanically removing small plugs of soil from a lawn or other ground surface. Aeration is typically performed in a relatively limited portion of the year, spanning several weeks in the spring and several weeks in the fall. Because the aeration season is short, commercial landscapers need robust aeration equipment to maximize productivity.
Commercial landscapers commonly employ mechanical, self-propelled power aerators (“aerators”) that allow an operator to ride or stand on the aerator. A typical aerator has tines, which are cutting members for removing plugs of soil during aeration. The tines are typically mounted on one or more rotating tine wheels. An aerator is typically powered by an internal-combustion engine that drives a chain operatively connected to propulsion wheels and the tine wheels.
One issue inherent in self-propelled aerators and other self-propelled power tools is the tendency for the chain or other flexible drive member to stretch, break, or otherwise need service, such as a manual tension adjustment. When a repair or service is needed, the resulting down time reduces productivity. Many existing aerators and other self-propelled power tools require frequent, manual, invasive service to adjust the tension in the chain or other flexible drive member. With respect to aerators, because it is difficult to predict when a chain tension adjustment is needed, the chain-and-sprocket systems of aerators are prone to failure due to failure to adjust the tension. In addition, the dynamics of the chain drive or other flexible drive member of a self-propelled power tool can cause vibrations and variations in tension, as well as variations in axle and shaft loads.
The presently preferred embodiment of the invention uses a spring-loaded tension mechanism to adjust to dynamic loading, wear, and break-in of chains and other flexible drive members and of sprockets, pulleys, and the like, without the need for manual service of the tension control mechanism. The tension control mechanism also provides for appropriate tension when the self-propelled power tool is driven in reverse. The presently preferred embodiment of the invention does not require the user or owner to have service performed in order to maintain proper tension. The presently preferred embodiment of the tension control mechanism maintains tension automatically and includes a ratchet that adjusts the tension to compensate for normal wear and break-in.